Ferroelectric field effect in ultrathin SrRuO3 films

Ahn, Charles; Hammond, R. H.; Geballe, T. H.; Beasley, M. R.; Triscone, Jean‐Marc; Decroux, M.; Fischer, Ø.; Antognazza, L.; Char, K.

doi:10.1063/1.118203

Cited by 106 publications

(76 citation statements)

References 10 publications

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“…19 Therefore a stability of the SrRuO 3 thin films is rather limited. The films are stable when a deposition or a treatment proceeds in oxygen containing ambience within certain limits of an oxygen partial pressure and temperature.…”

Section: Introductionmentioning

confidence: 99%

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Surface layer of SrRuO3 epitaxial thin films under oxidizing and reducing conditions

Młynarczyk

Szot

Petraru

et al. 2007

Journal of Applied Physics

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Imperfect stoichiometry and heterogeneity of a surface layer of SrRuO3 epitaxial thin films, grown on SrTiO3 substrates, are presented with the help of various methods. Rutherford backscattering spectroscopy, x-ray photoemission spectroscopy (XPS), and time of flight secondary ion mass spectrometry are used to obtain information about the stoichiometry and uniformity of the SrRuO3 structure. The temperature of chemical decomposition is first determined for polycrystalline samples under different conditions using thermogravimetry analysis. Then the determined values are used for thin film annealings in high and low oxygen pressure ambients, namely, air, vacuum, and hydrogen. The surface deterioration of the thin film together with changes in its electronic structure is investigated. O1s and Sr3d core lines measured by XPS for as-made samples obviously consist of multiple components indicating different chemical surroundings of atoms. Thanks to different incident beam angle measurements it is possible to distinguish between interior and surface components. Valence band spectra of the interior of the film are consistent with theoretical calculations. After annealing, the ratio of the different components changes drastically. Stoichiometry near the surface changes, mostly due to ruthenium loss (RuOX) or a segregation process. The width and position of the Ru3p line for as-made samples suggest a mixed oxidation state from metallic to fully oxidized. Long annealing in hydrogen or vacuum ambient leads to a complete reduction of ruthenium to the metallic state. Local conductivity atomic force microscopy scans reveal the presence of nonconductive adsorbates incorporated in the surface region of the film. Charge transport in these measurements shows a tunneling character. Scanning tunneling microscopy scans show some loose and mobile adsorbates on the surface, likely containing hydroxyls. These results suggest that an adequate description of a SrRuO3 thin film should take into account imperfections and high reactivity of its surface region.

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Section: Introductionmentioning

confidence: 99%

“…Its extreme thermal, chemical, and electrical stability [19][20][21] would allow deposition, cleaning, and utilization using any standard procedure, under virtually any possible conditions. In fact it is well known that under oxidizing conditions ruthenium forms RuO 4 oxide which is volatile.…”

Section: Introductionmentioning

confidence: 99%

Surface layer of SrRuO3 epitaxial thin films under oxidizing and reducing conditions

Młynarczyk

Szot

Petraru

et al. 2007

Journal of Applied Physics

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“…4 In thin films, SRO is intensely investigated as a possible route to the realization of novel field-effect devices. 5,6 In addition, it is of particular interest to the spintronic 7,8 and multiferroic 9,10 communities, which have been recently energized by the possible device applications available from engineering interface phenomena. [11][12][13][14][15][16][17] However, one limitation in the design of thin film oxide devices is the observation of increased resistivity in metal oxides as the film thickness decreases.…”

Section: Introductionmentioning

confidence: 99%

Electronic properties of bulk and thin filmSrRuO3: Search for the metal-insulator transition

et al. 2008

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We calculate the properties of the 4d ferromagnet SrRuO 3 in bulk and thin film form with the aim of understanding the experimentally observed metal-to-insulator transition at reduced thickness. Although the spatial extent of the 4d orbitals is quite large, many experimental results have suggested that electron-electron correlations play an important role in determining this material's electronic structure. In order to investigate the importance of correlation, we use two approaches which go beyond the conventional local-density approximation to density-functional theory ͑DFT͒: the local spin-density approximation+ Hubbard U ͑LSDA+ U͒ and the pseudopotential self-interaction correction ͑pseudo-SIC͒ methods. We find that the details of the electronic structure predicted with the LSDA do not agree with the experimental spectroscopic data for bulk and thin film SrRuO 3 . Improvement is found by including electron-electron correlations, and we suggest that bulk orthorhombic SrRuO 3 is a moderately correlated ferromagnet whose electronic structure is best described by a 0.6 eV on-site Hubbard term, or equivalently with corrections for the self-interaction error. We also perform ab initio transport calculations that confirm that SrRuO 3 has a negative spin polarization at the Fermi level, due to the position of the minority Ru 4d band center. Even with static correlations included in our calculations we are unable to reproduce the experimentally observed metal-insulator transition, suggesting that the electronic behavior of SrRuO 3 ultrathin films might be dominated by extrinsic factors, such as surface disorder and defects, or due to dynamic spin correlations which are not included in our theoretical methods.

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“…We choose SrRuO 3 /SrTiO 3 heterostructures as our representative system, motivated by the favorable dielectric properties of SrTiO 3 (STO) 16 and the widespread use of thin film ferromagnetic SrRuO 3 (SRO) as oxide electrodes 17 ; furthermore, the effects of interfacial carrier modulation in thin films of both materials have been intensively investigated as a possible route to the realization of novel field-effect devices 18,19 . We note that our conclusions are not specific to this system but should apply to any dielectric/magnetic metal interface.…”

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confidence: 99%

Carrier-mediated magnetoelectricity in complex oxide heterostructures

2007

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The search for a general means to control the coupling between electricity and magnetism has intrigued scientists since Ørsted's discovery of electromagnetism in the early 19 th century.While tremendous success has been achieved to date in creating both single phase and composite magnetoelectric materials, the quintessential electric-field control of magnetism remains elusive.In this work, we demonstrate a linear magnetoelectric effect which arises from a novel carriermediated mechanism, and is a universal feature of the interface between a dielectric and a spinpolarized metal. Using first-principles density functional calculations, we illustrate this effect at the SrRuO 3 /SrTiO 3 interface and describe its origin. To formally quantify the magnetic response of such an interface to an applied electric field, we introduce and define the concept of spin capacitance. In addition to its magnetoelectric and spin capacitive behavior, the interface displays a spatial coexistence of magnetism and dielectric polarization suggesting a route to a new type of interfacial multiferroic.

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Ferroelectric field effect in ultrathin SrRuO3 films

Cited by 106 publications

References 10 publications

Surface layer of SrRuO3 epitaxial thin films under oxidizing and reducing conditions

Surface layer of SrRuO3 epitaxial thin films under oxidizing and reducing conditions

Electronic properties of bulk and thin filmSrRuO3: Search for the metal-insulator transition

Carrier-mediated magnetoelectricity in complex oxide heterostructures

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